The purpose of a pile foundation is to move and distribute a load through a material or layer that has a strong stratum with insufficient bearing, sliding or hoisting capacity capable of supporting the load without damaging displacement. A wide range of pile types are available for applications with a variety of soil and structural requirements. So before we delve deeper into selecting the appropriate type of heap, let’s take a look at some of the common heap types and their characteristics.

Features of common heap types

(1) Steel H-piles

Steel H-piles have significant advantages over other types of piles. They can provide high axial work efficiency in excess of 400 kips. They can be obtained in a variety of sizes and lengths and can be easily handled, split and cut. H-piles displace smaller soils and are much easier to drive. They can penetrate obstacles better than most piles, with less damage to piles from bumps or hard driving. The major disadvantages of steel H-piles are the high material cost for steel and the potentially long delivery time for mill orders. Unless preventive measures are used, H-piles can be subject to extreme corrosion in some environments. Pile shoes are required when driving in dense sand levels, gravel levels, cobble-boulder zones, and when driving refuse piles over a hard layer of pile.

(2) Steel Pipe Piles

Steel pipe piles can be run open or closed end and filled with concrete or left unfinished. Concrete-filled pipe piles can provide very high load capacities, in some cases over 1,000 kips.

Pipe piles are more difficult to install than H-piles because closed-end piles displace more soil, and open-ended pipe piles form a soil plug at the bottom and act like a closed-end pile . Handling, splicing and cutting are easy. Pipe piles have the same disadvantages as H-piles (ie, higher steel costs, longer delivery times, and potential corrosion problems).

(3) Precast concrete pile

Precast concrete piles are usually pre-stressed for driving and stress handling. Axial load capacity can reach 500Kips or more. They have high load capacity as abrasive piles in sand or where tip bearing on soil is important. Concrete piles are generally durable and corrosion resistant and are often used where the pile must be above ground. However, durability is also a problem with precast concrete piles in some saltwater applications. Tall piles are more difficult to handle and drive precast concrete piles than steel piles. For pre-stressed piles, cutting is much more important when the required length is not precisely known, and splicing is more difficult to transfer tensile and lateral forces from the pile head to the base slab.

(4) Cast-in-Place Concrete Piles

Cast-in-Place Concrete Pile Thin shell pipe consists of shafts of cast concrete, driven from above into the soil, and usually has closed ends. Such piles can provide up to 200-kip capacity. The main advantage over precast piles is the ease of changing the length by cutting or splitting the shell. The material cost of cast-in-place piles is relatively low. They are not possible when driving through hard soil or rock.

(5) mandrel-driven piles

Mandrel-powered piles are thin steel balls that are driven into the ground with a mandrel and then filled with concrete. Such piles can provide up to 200-kip capacity. The disadvantage is that while this type of pile usually requires a patent, the franchising system for installation and installation is not as simple as for steel or precast concrete piles. They offer the advantage of lower steel cost as thinner materials can be used in the case of top-driven piles. The heavy mandrel makes the high capacity possible.

Increasing the length of mandrel-driven piles can be very difficult because the maximum length of pile that can be operated is limited by the length of mandrel available on site. Contractors may claim additional cost for bringing a longer mandrel to the site if necessary.

(6) Timber Piles

Wood piles are relatively inexpensive, small, low-capacity piles. Long Douglas fir piles are available but they will be more expensive. They may be desirable in some applications such as special types of corrosive groundwater. Loads are usually limited to 70 kips. Stacks are very convenient to handle. Untreated wood piles are susceptible to decay, insects and borers in some environments. They are easily damaged during hard driving and are inconvenient to connect.

Initial selection of heap type

All identified foundation options must first be evaluated for suitability for the intended application and cost. For hemorrhoids, this evaluation should be based on: Capacity, availability, manufacturing capacity, and expected Display From a plethora of different types. The initial evaluation of non-stack options should be based on the same criteria. This would limit further study to foundation options that are reasonably feasible. During this initial evaluation, it may also be possible to consider alternatives with obvious higher costs.

(1) load capacity and pile spacing

The main importance is the load bearing capacity of piles. In determining the capacity of a pile foundation, it is important to consider the pile spacing along with the capacity of the individual piles. The lateral load resistance of piles can also be important because lateral loads can induce high bending stresses in the pile.

(2) manufacturing capacity

The effect of anticipated subsurface and surface impacts on construction efficiency should be considered. Piles prone to damage during hard driving are less likely to penetrate hard straights or gravel and boulder zones. Soil disturbance or transmission of driving vibrations during construction can damage adjacent piles or structures. Pile spacing and battens must be selected to prevent interference with other structural components during driving. The ease of cutting or splitting piles can also affect buildability.

(3) performance

Pile foundations must perform as designed for the life of the structure. Performance can be described in terms of structural displacement which can be as damaging to the structure as a true pile failure. The load capacity should not decrease over time due to wear of the pile material.

(4) Availability

The pile must be available in the required length, or they must be split or cut. Project scheduling can make lead time an important consideration, as some piles may require up to 6 months between order and delivery.

(5) cost

Once heap type meets all other criteria, relative cost becomes a major consideration. For comparisons between types of piles, comparing pile cost per load capacity may suffice. Comparisons between unit capacity costs may lead to the explicit exclusion of some heap types. The cost appraisal should include all expenses related to and dependent on the pile foundation. Such costs may include additional expenses for storage or splicing. They may include pressure-relief systems that are used to reduce uplift pressures and thus control pile loads. In addition, any necessary modifications to the structure to accommodate the stack should be included in the comparative cost estimate. For example, an increase in base slab thickness may be required to provide additional embedding for the top of the pile.

final selection of heap type

The final evaluation and selection should be based primarily on the relative cost of the remaining alternatives. This appraisal should include the cost of structural or site modifications needed to accommodate the type of foundation. Cost and other factors can be important in the selection. Differences in delivery or installation schedules, performance reliability levels, and potential construction complications may all be considered.

When comparing a pile foundation to any other type of foundation, it will be necessary to develop a preliminary pile layout to determine a reasonable estimate of quantity.

Er. Mukesh Kumar

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Er. Mukesh Kumar is Editor in Chief and Co-Funder at Civil Engineering Website. Mukesh Kumar is a Bachelor in Civil Engineering From MIT. He has work experience in Highway Construction, Bridge Construction, Railway Steel Girder work, Under box culvert construction, Retaining wall construction. He was a lecturer in a Engineering college for more than 6 years.